The copending application of Frederik Theijsmeijer, Ser. No. 816,243, filed July 18,1977 now U.S. Pat. No. 4,150,584 discloses an improved block and bar chain of the trolley conveyor type which includes a center link having an improved U-shaped bushing at each end of the link. The bushing with the center link is respectively turnable on the pin; the center link is pivotable on either bushing about a separate axis normal to that of the pins. The improved double flexure of the chain reduces the stress in the chain parts comprising the joint and in turn allows the center link and the bushings in particular to be of a molded plastic construction of the required configuration. The inserts have pivot and retaining means and their plastic construction permits their "snap-in" assembly.
A desireable characteristic of this improved, lightweight chain is the ease of its assembly and disassembly. However, in handling a long assembled length of such lightweight chain, two adjacent links at any joint may readily become so arranged that the pin falls out. This then requires the reassembly of the chain at that joint.
The object of the present invention was first to provide a simple, reliable means of overcoming this problem in such chain. A further object is to provide a chain pin bushing generally with detent means for that purpose. A more general object is to provide such detent means for that purpose also in similar chain which does not include such a bushing.